May 16, 2014: This photo shows the General Motors logo at the company's world headquarters in Detroit. (AP Photo/Paul Sancya, File)

An internal probe of General Motors Co.'s delay in recalling defective cars is expected to conclude there was no concerted cover-up, but that managers operating in isolation failed to make connections and act on evidence of problems now linked to fatal accidents, people familiar with the situation said.

GM Chief Executive Mary Barra on Thursday is expected to outline new steps to overhaul GM's culture and management, including the departures of more employees, when she publicly presents the investigative findings by former U.S. prosecutor Anton Valukas, those people said.

GM is expected to announce the dismissal of "a number of people," including the engineer who designed the switch, Raymond DeGiorgio and some members of the company's legal department, people familiar with the matter said. General Counsel Michael Millikin is staying on, people familiar with the situation said late Wednesday. The Valukas report absolves Mr. Millikin of responsibility for the mishandling of safety defects and the delay of recalls, two people familiar with the report said. Mr. DeGiorgio couldn't be reached for comment Wednesday.

The probe is expected to conclude that Ms. Barra, her direct reports, the board and former CEO Dan Akerson were unaware before December 2013 of defective ignition switches installed in as many as 2.6 million cars, said people familiar with the findings.

Switches could abruptly slip out of the run position, disabling air bags and cutting the power assistance for steering and brakes. Documents provided to Congress by the nation's largest auto maker show that some of its employees knew about the problem as early as 2001, and that in 2004 and 2005 managers decided not to redesign the switches because of the cost.

GM's board likely will create a new operational risk-management committee to more closely monitor how top executives handle potential risks, especially on the manufacturing side, two people said.

According to GM's latest proxy statement, five current board committees keep tabs on risk-related issues but none seem specifically responsible for operational risks. Top management will "have clear lines of reporting" to such a panel, a person said.